Relative Dielectric Permittivity Variations during Compaction as a Mean of Compaction Quality Control: Case Study on Laterite Samples from Senegal

This study explores an alternative to the classical use of direct methods, as water content and dry density measurements, for compaction quality control. For this purpose, the dielectric properties of lateritic materials are determined by radar method and are compared with the permittivity determined from the Topp formula and from the CRIM model. This approach allowed to establish a relationship between the geotechnical properties determined during compaction such as dry density, water content or porosity with dielectric permittivity. The obtained results made it possible to determine an optimum dielectric permittivity corresponding to the optimum dry density and the optimum water content that could be used for non-destructive in situ compaction testing. Such an approach should improve the implementation and effectiveness of in situ compaction quality control of geotechnical infrastructures.

Dielectric Permittivity of Rigid Rapeseed Oil Polyol Polyurethane Biofoams and Petrochemical Foams at Low Frequencies

Early investigations of dielectric permittivity of rigid polyurethane foams at low frequencies were made on petrochemical-origin foams,mainly by means of parallel plate capacitors.In the present investigation biopolyol was synthesized from Latvia-grown rapeseeds’oil by the transesterification method with triethanolamine,in an environmentally friendly process,without emission of harmful substances,at temperatures 175℃±5℃.Rigid,closed-cell rapeseed oil polyol polyurethane biofoams and petrochemical foams were made ensuring content of the renewable rapeseed oil polyol in ready foams 27 wt.%–29 wt.%.Dielectric permittivity of the polyurethane foams and the underlying monolithic petrochemical-origin polyurethane and biopolyurethane was measured with a non-destructive dielectric spectrometer equipped with a capacitive sensor of one-side access type at 16 discrete frequencies distributed geometrically over the band 10 Hz,…,330 kHz.Permittivity value of the gaseous phase in the closed-cells was estimated to beεg≈1.001 that corresponds to the values,characteristic for the most of gases.Dielectric permittivity of petrochemical polyurethane foams and the mentioned biofoams was compared with permittivity of polyurethane foams from industrial producers Sika JSC and General Plastics Manufacturing Co.Polyurethane foams of the developed formulation exhibit competitive,low dielectric permittivity,not exceeding that of the foams from industrial producers:petrochemical foams up to 550 kg/m^(3) and the mentioned biofoams,comprising the renewable rapeseed oil polyol,up to densities 230–250 kg/m^(3).Considering petrochemical-origin polyurethane foams as a heterogeneous media“Polymer—gaseous phase”,the applicability of the rule of mixture and Maxwell–Garnett equation to model mathematically the dependence of effective dielectric permittivity on the volume fraction of phases was showed.

Wide-Temperature-Range Dielectric Permittivity Measurement under High Pressure

Two measurement systems are developed for in-situ dielectric property measurement under high pressure in a wide-temperature range from 77K to 1273 K. The high-temperature system ranging from room temperature up to 1273K is equipped with a hexahedron anvils press, while the low-temperature system ranging from liquid nitrogen temperature to normal condition is equipped using the piston cylinder setup with a specially designed sample chamber. Using these configurations, the dielectric property measurement of ferroelectrie BaTiO3 and multiferroie Tm0.5Gd0.5MnO3 compounds are demonstrated, which proves the validity of the systems through the tuning of the polarization and phase transition boundary by high pressure. These two systems will be equally applicable to a wide variety of electronic and transport property measurements of insulators, semiconductors, as well as battery materials.

A New Numerical Method for Calculation of Complex Dielectric Permittivity

In this paper, a new numerical method-Kuhn algorithm with contour integral-is intrroduced and used to calculate the complex dielectric permittivities of materials from the short-circuitedwaveguide measurements. Some numerical results are given to verify the validity and efficiency ofthe new numerical method and the complex dielectric permittivities of materials calculated by thenew numerical method are quite identical with the results given by other works.

Dielectric permittivity of dusty plasma in the Earth's mesosphere

This paper deals with the dielectric permittivity of dusty plasma in the earth’s mesosphere.We give expressions for the complex dielectric permittivity of dusty plasma,taking into account the effects of the dust charging process and magnetic field.We discuss the dielectric permittivity of dusty plasma in several cases,such as high frequency approximation,parallel propagation in MF/HF band,and effects of plasma movement.Finally,the expressions are employed to study the phenomenon of radar echoes from the polar summer mesosphere.We report that dielectric permittivity caused by the dust charging process gives a radar cross section proportional to ω–4 and produces a number density of charged dust that agrees with measurements of mesopheric radar echoes.

Low temperature sintered giant dielectric permittivity CaCu_(3)Ti_(4)O_(12) sol-gel synthesized nanoparticle capacitors

This paper reports on synthesis of polycrystalline complex perovskite CaCu_(3)Ti_(4)O_(12)(as CCTO)ceramic powders prepared by a sol–gel auto combustion method at different sintering temperatures and sintering times,respectively.The effect of sintering time on the structure,morphology,dielectric and electrical properties of CCTO ceramics is investigated.Tuning the electrical properties via different sintering times is demonstrated for ceramic samples.X-ray diffraction(XRD)studies confirm perovskite-like structure at room temperature.Abnormal grain growth is observed for ceramic samples.Giant dielectric permittivity was realized for CCTO ceramics.High dielectric permittivity was attributed to the internal barrier layer capacitance(IBLC)model associated with the Maxwell–Wagner(MW)polarization mechanism.

Dipole relaxation process and giant dielectric permittivity in Eu3þdoped CdMoO_(4) single crystal

Single crystal of Eu3þ-doped cadmium molybdate(Cd0.9268M0.0244Eu0.0488MoO_(4),where M denotes cationic vacancies)has been successfully grown by the Czochralski method in air and under 1 MPa.X-ray diffraction analysis indicates that as-grown single crystal exhibits tetragonal scheelite-type structure(a=b=5.16188(14)Å;c=11.2080(5)Å;space group I41/a).Eu^(3+) þions do not show long-range order and they are randomly distributed in CdMoO_(4) framework substituting Cd^(2+ )þones.UVevis diffuse reflectance measurements revealed very close optical band gap(Eg)values,i.e.-1.74 eV along[100]and[001]crystallographic directions that are twice smaller than Eg of microcrystalline pure CdMoO_(4) as well as powder Eu3þ-doped single crystal.Magnetic and electrical studies of Eu3þ-doped cadmium molybdate single crystal showed a paramagnetic and n-type semiconducting behaviour with the metal-insulator transition above 350 K along both crystallographic directions.Dielectric results analysis using the Cole-Cole fit function revealed that the dipole relaxation process has different time scale depending on the crystallographic direction and exhibits Arrhenius temperature dependence for both studied directions.This fact is accompanied by the colossal dielectric permittivity withεr>8,103.The above results are considered in the framework of narrow europium multiplets of energy comparable to thermal energy.

CONTRIBUTION OF THE INTERPHASE INTERACTION TO THE DIELECTRIC PERMITTIVITY OF COLLOID SYSTEMS

Specific features of the dielectric response of colloid systems with electrically interacting com-ponents(polar liquid matrix and solid spherical inclusions)have been revealed.A theory was developed to describe dielectric dispersion and anisotropy of the liquid phase caused by the electric field of surface charges on the solid particles.It was found that the local dielectric permittivity in diferent directions can vary over a wide range and strongly depends on the strength of the inner field.The existence of the interphase interaction leads to the formation of thin structured liquid layers in the contact area of two phases and,therefore,to a decrease in the average dielectric permittivity of the considered system.Nonuniform structure of the polar liquid was taken into account while the derivation of a mixing formula which clearly demonstrates the contribution of the interphase interaction to the dielectric response of the investigated colloid system.

Temperature characterization of dielectric permittivity and AC conductivity of nano copper oxide-doped polyaniline composite

The polyaniline/copper oxide(PANI/CuO)nanocomposite was prepared by mixing solutions of polyaniline and copper oxide nanoparticles in dimethyl sulfoxide(DMSO).The synthesized polymer nanocomposites were characterized by X-ray powder diffraction(XRD),scanning electron microscope(SEM)and UV-visible spectroscopy.The characteristic peaks in XRD and UV-visible spectra confirmed the presence of CuO in the polymer structure.SEM images indicated morphological changes in the composite matrix as compared to the pristine PANI.The DC conductivity measurements were performed using two-probe method for various temperatures.AC conductivity and dielectric response of the composites were investigated in the frequency range of 10^(2)-10^(6)Hz using LCR meter.Dielectric permittivity
ε′(w)and dielectric loss factor
ε″(w)were investigated.It was observed thatε′(w)and
ε″(w)decrease with increase in frequency at all temperatures.At a particular frequency it is observed that bothε′(w)andε″(w)increase with increase in temperature.It was also observed that AC conductivity increased with increase in frequency and temperature.

A Short Review on Copper Calcium Titanate(CCTO) Electroceramic;Synthesis,Dielectric Properties,Film Deposition,and Sensing Application

Electroceramic calcium copper titanates(CaCu3Ti4O12,CCTO),with high dielectric permittivities（e） of approximately 105 and 104,respectively,for single crystal and bulk materials,are produced for a number of wellestablished and emerging applications such as resonator,capacitor,and sensor.These applications take advantage of the unique properties achieved through the structure and properties of CCTO.This review comprehensively focuses on the primary processing routes,effect of impurity,dielectric permittivity,and deposition technique used for the processing of electroceramics along with their chemical composition and micro and nanostructures.Emphasis is given to versatile and basic approaches that allow one to control the microstructural features that ultimately determine the properties of the CCTO ceramic.Despite the intensive research in this area,none of the studies available in the literature provides all the possible relevant information about CCTO fabrication,structure,the factors influencing its dielectric properties,CCTO immobilization,and sensing applications.

Microstructural,magnetic and dielectric performance of rare earth ion(Sm^(3+))-doped MgCd ferrites

The combined effects of Sm^(3+)substitution together with the addition of 3 wt%Bi_(2)O_(3)endow Mg Cd ferrites with excellent magnetic permeability and dielectric permittivity.Various concentrations of Sm^(3+)(x=0,0.03,0.06,0.09,0.12and 0.15)were employed to modify the permeability(μ)and permittivity(ε)of the Mg Cd ferrites.X-ray diffraction,scanning electron microscopy(SEM),vibrating sample magnetometry and vector network analysis techniques were used to characterize the samples.The measurement results reveal that the ferrites processed a saturation magnetization of up to 36.8 emu/g and coercivity of up to 29.2 Oe via the conventional solid-state reaction method.The surface morphology SEM confirms that with increasing Sm^(3+)concentration,the grain shape changes from a polygon to a circle.Moreover,the dielectric permittivity can reach a value of 23.The excellent properties obtained in Sm^(3+)-substituted Mg ferrites suggest that they could be promising candidates for modern high-frequency antenna substrates or multilayer devices.

Comprehensive studies on dielectric properties of p-methoxy benzylidene p-decyl aniline with function of temperature and frequency in planar geometry: A potential nematic liquid crystal for display devices

The dielectric properties of the nematic mesophase, p-methoxy benzylidene p-decyl aniline(MBDA), measured in planar geometry with a function of frequency and temperature are investigated in detail. The complex dielectric permittivity(ε' and ε'') is also studied at a bias voltage of 10 V for planar aligned sample cell of nematic mesophase. The dielectric permittivity with bias voltage attains a higher(> 2 times) value than that without bias voltage at a temperature of 56℃,which is due to the fact that the linking group of nematic molecules is internally interacted with an applied bias voltage.This is supported by observing an enhanced dielectric permittivity of nematic liquid crystal(LC) in the presence of bias voltage, which can be fully explained as the increasing of the corresponding dipole moment. The dielectric relaxation behaviors of nematic LC are also demonstrated for planar aligned sample cell. The remarkable results are observed that the relaxation frequency shifts into low frequency region with the increase of the bias voltage applied to the planar aligned sample cells. The dielectric relaxation spectra are fitted by Cole–Cole nonlinear curve fitting for nematic mesophase in order to determine the dielectric strength.

Electrical Relaxation in Mixed Alkali Bi_2O_3-K_2O-Li_2O-Fe_2O_3 Glasses

A new glass system （Bi2O3）50（Fe2O3）10（Li2O）x（K2O）40-x, where x changes in steps of 5 mole fraction between 0 and 40, was selected to study the electrical relaxation and the mixed alkali effect （MAE） phenomena. Measurements of ac conductivity σac, dielectric permittivity ε′ and loss factor tanδ in the frequency range of 0.12～10^2 kHz and in the temperature range of 300～650 K were carried out. The temperature dependence of the ac conductivity shows a slow increasing rate at low temperature and high frequency and a rapid increase at high temperature and low frequency. At constant temperature, the ac conductivity is found to be proportional to ω^8, where s is the frequency exponent, which is less than 1. Analysis of the conductivity data and the frequency exponent shows that the overlapping large polaron tunnelling （OLPT） model of ions is the most favorable mechanism for the ac conduction in the present glass system. The ac response, the dc conductivity and dielectric relaxation have the same activation energy and they originate from the same basic transport mechanism. The results of the dielectric permittivity show no maximum peak in the temperature and frequency range studied. This absence of maximum peak is an indication of non-ferroelectric behavior of all the studied samples. The MAE has been detected in the ac conductivity, which is the same as the classical MAE in the dc conductivity. The electrical parameters such as dielectric permittivity ε′ and real dielectric modulus M′ show a typical minimum deviation from linearity by about two orders of magnitude. The loss factor tanδ and the imaginary dielectric modulus M″ are insignificantly dependent on composition even at the same transition temperature Tg.

Novel attributes and design considerations of effective oxide thickness in nano DG MOSFETs

Impacts of effective oxide thickness on a symmetric double-gate MOSFET with 9-nm gate length are studied, using full quantum simulation. The simulations are based on a self-consistent solution of the two-dimensional （2D） Poisson equation and the Schr6dinger equation within the non-equilibrium Green＇s function formalism. Oxide thickness and gate dielectric are investigated in terms of drain current, on-off current ratio, off current, sub-threshold swing, drain induced barrier lowering, transconductance, drain conductance, and voltage. Simulation results illustrate that we can improve the device performance by proper selection of the effective oxide thickness.

Lattice dynamics properties of chalcopyrite ZnSnP_2:Density-functional calculations by using a linear response theory

We present a first-principles study of the structural,dielectric,and lattice dynamical properties for chalcopyrite semiconductor ZnSnP2.The structural properties are calculated using a plane-wave pseudopotential method of densityfunctional theory.A linear response theory is used to derive Born effective charge tensors for each atom,dielectric constants in low and high frequency limits,and phonon frequencies.We calculate all zone-center phonon modes,identify Raman and infrared active modes,and report LO-TO splitting of the infrared modes.The results show an excellent agreement with experiment and propose several predictive behaviors.

PROPAGATION OF ELECTROMAGNETIC WAVE IN THE THREE PHASES SOIL MEDIA

The fundamental parameters such as dielectric permittivity and magnetic permeability are required to solve the propagation of electromagnetic wave (EM Wave) in the soil. Based on Maxwell equations, the equivalent model is proposed to calculate the dielectric permittivity of mixed soil. The results of calculation fit the test data well and will provide solid foundation for the application of EM wave in the soil moisture testing,CT analyzing of soil and the inspecting of geoenvironment.

Field-induced phase transitions in chiral smectic liquid crystals studied by the constant current method

In ferroelectric liquid crystals, phase transitions can be induced by an electric field. The current constant method allows these transition to be quickly localized and thus the（E, T） phase diagram of the studied product can be obtained.In this work, we make a slight modification to the measurement principles based on this method. This modification allows the characteristic parameters of ferroelectric liquid crystal to be quantitatively measured. The use of a current square signal highlights a phenomenon of ferroelectric hysteresis with remnant polarization at null field, which points out an effect of memory in this compound.

Phenomena in Polarized Disperse Systems Caused by Exchange-Correlation Interaction between Particles

We have studied the self-consistent states of nano- and micro-particle polarized powders and structures consisting of parallel particle chains and have determined conditions under which the static dielectric permittivity of a disperse system is negative. It has been shown that in such system an electric current runs without ohmic losses. We present the arguments for the physics of spontaneous emergence of the electric field in disperse systems made up of electrically neutral particles. It has been determined the influence the phase boundaries of a disperse system has on the origin of spontaneous polarization state. The structures consisting of parallel chains of dielectric particles can exhibit spontaneous polarization. In this case the properties of the spherical structure are similar to those of the ball lightning. It has been established correspondence of the obtained theoretical results with the experimental data available in the literature.

Analytical threshold voltage model for strained silicon GAA-TFET

Tunnel field effect transistors（TFETs） are promising devices for low power applications.An analytical threshold voltage model,based on the channel surface potential and electric field obtained by solving the 2D Poisson＇s equation,for strained silicon gate all around TFETs is proposed.The variation of the threshold voltage with device parameters,such as the strain（Ge mole fraction x）,gate oxide thickness,gate oxide permittivity,and channel length has also been investigated.The threshold voltage model is extracted using the peak transconductance method and is verified by good agreement with the results obtained from the TCAD simulation.

Enhanced thermal conductivity and dielectric properties in electrostatic self-assembly 3D pBN@nCNTs fillers loaded in epoxy resin composites

High-performance epoxy(EP)composites with excellent thermal conductivity and dielectric properties have attracted increasing attention for effective thermal management.In this work,three-dimensional(3D)structural functional fillers were prepared by an electrostatic self-assembly approach.The negatively charged carbon nanotubes(nCNTs)prepared by carboxylation on the surface of CNTs were attached to the positively charged boron nitride(pBN)to form the 3D pBN@nCNTs functional fillers.The morphological characterizations of the formed 3D pBN@nCNTs fillers and epoxy composites were established,illustrating that nCNTs were linearly overlapped between the BN sheets,thus forming a 3D heat conduction network in the epoxy matrix.The synergistic effect of pBN with nCNTs on the enhancement of thermal conductivity and dielectric properties of composites was systematically studied.The experimental results demonstrated that the thermal conductivity of pBN@nCNTs/EP composites could reach 1.986 W m1K1 with the loading of 50 wt%fillers at 10:1 mass ratio of pBN:nCNTs,which is 464%and 124%higher than that of pure EP and BN/EP,respectively.Simultaneously,the dielectric permittivity was successfully increased to 15.14.Moreover,the thermal stability of the composites was synchronously enhanced.This study provides a facile path to fabricate thermosetting polymer composites with high thermal conductivity and dielectric properties.